In the air separation unit, when the oxygen enrichment needs to reduce the output, the core regulation principle is: first stabilize the working condition, then reduce the output, anti-nitrogen plug, maintain the purity, control the pressure difference, and operate stably and orderly to avoid working condition disorder. The specific precautions are as follows:
First, reduce the air volume and then the oxygen output. It is forbidden to close only the oxygen outlet without reducing the air volume into the column. Gradually reduce the load of the air compressor or the air volume into the column to ensure that it matches the oxygen output and prevent the pressure rise of the upper column.
Second, the nitrogen plug on the column shall be strictly prevented, which is the key for adjustment. The decrease of oxygen output will easily cause the oxygen-enriched zone of the upper column to move upward. Therefore, it is necessary to appropriately increase the liquid nitrogen reflux or improve the liquid-air purity. Pay close attention to the purity of oxygen and nitrogen and the resistance of the upper column to avoid nitrogen mixing with oxygen products.
Third, stabilize the pressure and liquid level of the rectifying column. The control valve shall be operated slowly for a few times to prevent large fluctuation of the upper column pressure, argon fraction (in case of argon column), liquid air, liquid nitrogen and oxygen level. Coordinate with the control phase throttle valve to maintain the stability of rectification.
Fourthly, consider the argon system and outlet pressure. When there is an argon column, synchronously reduce the amount of argon withdrawn to avoid high nitrogen content of argon fraction; The oxygen outlet shall be stabilized first and then reduced to prevent impact on subsequent pipe network and users.
In addition, avoid long-time low-load operation, prevent reduction of rectification efficiency and increase of energy consumption, and adjust product structure or unit load for long-term reduction. Operation tips: first reduce air and then oxygen, stabilize pressure and stabilize liquid nitrogen proof plug, keep a close watch on purity liquid level, and synchronously adjust argon system.
